This invention relates to an improvement in a method of working for bending a metal material, such as iron plate or the like.
More particularly, this invention relates to the method of working for bending metal so that the bent portion is prevented from being rounded and is made substantially in rectangular shape.
Conventionally when a plate metal undergoes a 180.degree. bend, that is to two halves folded together, the folded edge becomes round and it was difficult to make it rectangular. When the metal piece undergoes a 180.degree. bend, that is folded to two halves close to each other, in such instance if the outer face of its bent portion is made to be rectangular so that its outer end is flat, this will have a better quality than that of the round end. That is, such flat portion will stand up against greater pressure and be wearproof. Therefore making of such flat end will be utilized in many situations matters.